Fix a regression on the disassembling C API.

The fix is easy. Unfortunately, we had 0 tests, so adding one was somewhat
complicated.

Thanks to Kevin Enderby for the report.

llvm-svn: 221899
diff --git a/llvm/lib/MC/MCDisassembler/Disassembler.cpp b/llvm/lib/MC/MCDisassembler/Disassembler.cpp
index 52c4664..d0d7f30 100644
--- a/llvm/lib/MC/MCDisassembler/Disassembler.cpp
+++ b/llvm/lib/MC/MCDisassembler/Disassembler.cpp
@@ -253,7 +253,7 @@
   MCDisassembler::DecodeStatus S;
   SmallVector<char, 64> InsnStr;
   raw_svector_ostream Annotations(InsnStr);
-  S = DisAsm->getInstruction(Inst, Size, Data, 0,
+  S = DisAsm->getInstruction(Inst, Size, Data, PC,
                              /*REMOVE*/ nulls(), Annotations);
   switch (S) {
   case MCDisassembler::Fail: